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Differential effects of mechano-electric feedback mechanisms on whole-heart activation, repolarization, and tension

JOURNAL OF PHYSIOLOGY-LONDON 2024年第18期602卷 4605-4624页

作者： Gerach, Tobias Loewe, Axel Karlsruhe Inst Technol KIT Inst Biomed Engn Karlsruhe Germany Karlsruhe Inst Technol KIT Inst Biomed Engn Kaiserstr 12 D-76131 Karlsruhe Germany

The human heart is subject to highly variable amounts of strain during day-to-day activities and needs to adapt to a wide range of physiological demands. This adaptation is driven by an autoregulatory loop that includes both electrical and the mechanical components. In particular, mechanical forces are known to feed back into the cardiac electrophysiology system, which can result in pro- and anti-arrhythmic effects. Despite the widespread use of computational modelling and simulation for cardiac electrophysiology research, the majority of in silico experiments ignore this mechano-electric feedback entirely due to the high computational cost associated with solving cardiac mechanics. In this study, we therefore use an electromechanically coupled whole-heart model to investigate the differential and combined effects of electromechanical feedback mechanisms with a focus on their physiological relevance during sinus rhythm. In particular, we consider troponin-bound calcium, the effect of deformation on the tissue diffusion tensor, and stretch-activated channels. We found that activation of the myocardium was only significantly affected when including deformation into the diffusion term of the monodomain equation. Repolarization, on the other hand, was influenced by both troponin-bound calcium and stretch-activated channels and resulted in steeper repolarization gradients in the atria. The latter also caused afterdepolarizations in the atria. Due to its central role for tension development, calcium bound to troponin affected stroke volume and pressure. In conclusion, we found that mechano-electric feedback changes activation and repolarization patterns throughout the heart during sinus rhythm and lead to a markedly more heterogeneous electrophysiological substrate.

关键词： computer modelling and simulation mechano-electric feedback monodomain repolarization gradient stretch-activated channels

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Proof of principle for template synthesis approach for the radio emission from vertical extensive air showers

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ASTROPARTICLE PHYSICS 2024年 157卷

作者： Desmet, Mitja Buitink, Stijn Huege, Tim Butler, David Engel, Ralph Scholten, Olaf Vrije Univ Brussel VUB Astrophys Inst Pl Laan 2 B-1050 Brussels Belgium Karlsruhe Inst Technol KIT Inst Astroparticle Phys POB 3640 D-76021 Karlsruhe Germany Univ Groningen RUG Kapteyn Astron Inst Landleven 12 NL-9747 AD Groningen Netherlands

The radio detection technique of cosmic ray air showers has gained renewed interest in the last two decades. While the radio experiments are very cost-effective to deploy, the Monte -Carlo simulations required to analyse the data are computationally expensive. Here we present a proof of concept for a novel way to synthesise the radio emission from extensive air showers in simulations. It is a hybrid approach which uses a single microscopic Monte -Carlo simulation, called the origin shower, to generate the radio emission from a target shower with a different longitudinal evolution, primary particle type and energy. The method employs semianalytical relations which only depend on the shower parameters to transform the radio signals in the simulated antennas. We apply this method to vertical air showers with energies ranging from 1017 eV to 1019 eV and compare the results with CoREAS simulations in two frequency bands, namely the broad [20, 500] MHz band and a more narrow one at [30, 80] MHz. We gauge the synthesis quality using the maximal amplitude and energy fluence contained in the signal. We observe that the quality depends primarily on the difference in Xmax between the origin and target shower. After applying a linear bias correction, we find that for a shift in Xmax of less than 150 g/cm2, template synthesis has a bias of less than 2% and a scatter up to 6%, both in amplitude, on the broad frequency range. On the restricted [30, 80] MHz range the bias is similar, but the spread on amplitude drops down to 3%. These fluctuations are on the same level as the intrinsic scatter we observe in Monte -Carlo ensembles. We therefore surmise the observed scatter in amplitude to originate from intrinsic shower fluctuations we do not explicitly account for in template synthesis.

关键词： Cosmic Rays Radio emission from extensive air showers computer modelling and simulation

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Virtual pacing of a patient's digital twin to predict left ventricular reverse remodelling after cardiac resynchronization therapy

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EUROPACE 2023年第1期26卷 euae009页

作者： Koopsen, Tijmen Gerrits, Willem van Osta, Nick van Loon, Tim Wouters, Philippe Prinzen, Frits W. Vernooy, Kevin Delhaas, Tammo Teske, Arco J. Meine, Mathias Cramer, Maarten J. Lumens, Joost Maastricht Univ CARIM Cardiovasc Res Inst Maastricht Dept Biomed Engn Univ Singel 40 NL-6200 MD Maastricht Netherlands Univ Med Ctr Utrecht UMCU Dept Cardiol Div Heart & Lungs Utrecht Netherlands Maastricht Univ CARIM Cardiovasc Res Inst Maastricht Dept Physiol Maastricht Netherlands Maastricht Univ CARIM Cardiovasc Res Inst Maastricht Dept Cardiol Maastricht Netherlands Maastricht Univ Med Ctr MUMC Dept Cardiol Maastricht Netherlands Radboud Univ Nijmegen Med Ctr Dept Cardiol Nijmegen Netherlands

Aims Identifying heart failure (HF) patients who will benefit from cardiac resynchronization therapy (CRT) remains challenging. We evaluated whether virtual pacing in a digital twin (DT) of the patient's heart could be used to predict the degree of left ventricular (LV) reverse remodelling post-CRT. Methods and results Forty-five HF patients with wide QRS complex (>= 130 ms) and reduced LV ejection fraction (<= 35%) receiving CRT were retrospectively enrolled. Echocardiography was performed before (baseline) and 6 months after CRT implantation to obtain LV volumes and 18-segment longitudinal strain. A previously developed algorithm was used to generate 45 DTs by personalizing the CircAdapt model to each patient's baseline measurements. From each DT, baseline septal-to-lateral myocardial work difference (MWLW-S,DT) and maximum rate of LV systolic pressure rise (dP/dt(max,DT)) were derived. Biventricular pacing was then simulated using patient-specific atrioventricular delay and lead location. Virtual pacing-induced changes Delta MWLW-S,DT and Delta dP/dt(max,DT) were correlated with real-world LV end-systolic volume change at 6-month follow-up (Delta LVESV). The DT's baseline MWLW-S,DT and virtual pacing-induced Delta MWLW-S,DT were both significantly associated with the real patient's reverse remodelling Delta LVESV (r = -0.60, P < 0.001 and r = 0.62, P < 0.001, respectively), while correlation between Delta dP/dt(max,DT) and Delta LVESV was considerably weaker (r = -0.34, P = 0.02). Conclusion Our results suggest that the reduction of septal-to-lateral work imbalance by virtual pacing in the DT can predict real-world post-CRT LV reverse remodelling. This DT approach could prove to be an additional tool in selecting HF patients for CRT and has the potential to provide valuable insights in optimization of CRT delivery. [GRAPHICS] .

关键词： In silico clinical trial Left bundle branch block CircAdapt Myocardial work Patient-specific modelling computer modelling and simulation

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On the mathematical modelling and data assimilation for air pollution assessment in the Tropical Andes

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ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 2020年第29期27卷 35993-36012页

作者： Quintero Montoya, O. L. Nino-Ruiz, Elias D. Pinel, Nicolas Univ EAFIT Math Modelling Res Grp Medellin Colombia Univ Norte Comp Sci Dept Barranquilla Colombia Univ EAFIT Biodivers Evolut & Conservat Medellin Colombia

Air pollution assessment in the Tropical Andes requires a multidisciplinary approach. This can be supported from the understanding of the underlying biological dynamics and atmospheric behavior, to the mathematical approach for the proper use of all available information. This review paper touches on several aspects in which mathematical models can help to solve challenging problems regarding air pollution in reviewing the state-of-the-art at the global level and assessing the corresponding state of development as applied to the Tropical Andes. We address the complexities and challenges that modelling atmospheric dynamics in a mega-diverse region with abrupt topography entails. Understanding the relevance of monitoring and facing the problems of data scarcity, we call attention to the usefulness of data assimilation for uncertainty reduction, and how these techniques could help tackle the scarcity of regional monitoring networks to accelerate the implementation and development of modelling systems for air quality in the Tropical Andes. Finally, we suggest a cyberphysical framework for decision-making processes based on the data assimilation of chemical transport models, the forecast of scenarios, and their use in regulation and policy making.

关键词： computer modelling and simulation Data assimilation and data analysis Biodiversity Conservation

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Electromechanical substrate characterization in arrhythmogenic cardiomyopathy using imaging-based patient-specific computer simulations

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EUROPACE 2021年第Sup1期23卷 I153-I160页

作者： van Osta, Nick Kirkels, Feddo Lyon, Aurore Koopsen, Tijmen van Loon, Tim Cramer, Maarten-Jan Teske, Arco J. Delhaas, Tammo Lumens, Joost Maastricht Univ Cardiovasc Res Inst Maastricht Dept Biomed Engn Univ Singel 50UNS50 NL-6229 ER Maastricht Netherlands Univ Med Ctr Utrecht Dept Cardiol Div Heart & Lungs Utrecht Netherlands

Aims Arrhythmogenic cardiomyopathy (AC) is an inherited cardiac disease, characterized by life-threatening ventricular arrhythmias and progressive cardiac dysfunction. The aim of this study is to use computer simulations to non-invasively estimate the individual patient's myocardial tissue substrates underlying regional right ventricular (RV) deformation abnormalities in a cohort of AC mutation carriers. Methods and results In 68 AC mutation carriers and 20 control subjects, regional longitudinal deformation patterns of the RV free wall (RVfw), interventricular septum (IVS), and left ventricular free wall (LVfw) were obtained using speckle-tracking echocardiography. We developed and used a patient-specific parameter estimation protocol based on the multiscale CircAdapt cardiovascular system model to create virtual AC subjects. Using the individual's deformation data as model input, this protocol automatically estimated regional RVfw and global IVS and LVfw tissue properties. The computational model was able to reproduce clinically measured regional deformation patterns for all subjects, with highly reproducible parameter estimations. simulations revealed that regional RVfw heterogeneity of both contractile function and compliance were increased in subjects with clinically advanced disease compared to mutation carriers without clinically established disease (17 +/- 13% vs. 8 +/- 4%, P=0.01 and 18 +/- 11% vs. 10 +/- 7%, P <0.01, respectively). No significant difference in activation delay was found. Conclusion Regional RV deformation abnormalities in AC mutation carriers were related to reduced regional contractile function and tissue compliance. In clinically advanced disease stages, a characteristic apex-to-base heterogeneity of tissue abnormalities was present in the majority of the subjects, with most pronounced disease in the basal region of the RVfw.

关键词： Arrhythmogenic right ventricular cardiomyopathy computer modelling and simulation Deformation imaging Contractility Right ventricle

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Pd-H and Ni-H phase diagrams using cluster variation method and Monte Carlo simulation

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PHILOSOPHICAL MAGAZINE 2019年第19期99卷 2376-2392页

作者： Bourgeois, Natacha Cenedese, Pierre Crivello, Jean-Claude Joubert, Jean-Marc UPEC CNRS ICMPE 2 Rue Henri Dunant F-94320 Thiais France

This work focuses on interstitial solid solutions of hydrogen in the face-centred cubic (fcc) host lattice of palladium and nickel, using a first-principles based approach. Cluster Variation Method (CVM) and Monte Carlo simulation algorithms were especially designed, allowing a coupled use of both techniques, to study hydrogen-vacancy interactions inside an fcc metallic host lattice. First-principles calculations provided the H-Vac interaction energies by structure inversion method. The phase diagrams and thermodynamic properties were computed using only theoretical inputs. The mechanisms leading to the formation of the miscibility gaps observed for both Pd-H and Ni-H systems and the hydrogen ordering on palladium interstitial lattice were reproduced without any empirical term.

关键词： Metal hydrides computer modelling and simulation miscibility gap

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Enlarge the biologic coating-induced absorbance enhancement of Au-Ag bimetallic nanoshells by tuning the metal composition

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SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018年 189卷 571-577页

作者： Zhu, Jian Li, Xin Li, Jian-jun Zhao, Jun-wu Xi An Jiao Tong Univ Sch Life Sci & Technol Minist Educ Key Lab Biomed Informat Engn Xian 710049 Shaanxi Peoples R China

Surface plasmon resonance (SPR) absorption properties of biologic layer-coated Au-Ag core-shell nanoparticle have been studied theoretically. By comparing with pure Au and Ag nanoparticles, the absorption peak intensity of Au-Ag bimetallic nanoparticle is more dependent on the dielectric coating, and the longer wavelength peak corresponding to the Au-Ag interface is more sensitive to the coating thickness. As the Au-Ag composition ratio is increased, the dielectric coating-dependent peak intensity change is always non-monotonous, and the critical Au-Ag composition ratio corresponding to the greatest peak intensity increase could be further tuned by changing the dielectric constant of the coated dielectric layer. The physical mechanism of the non-monotonous sensitivity change has been attributed to the Au-Ag composition ratio-dependent separation and overlap of the two SPR peaks from Au-Ag interface and outer Ag surface. These results indicate that the plasmonic absorption intensity of Au-Ag core-shell nanoparticle could be used in refractive index sensing and biologic detection. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Nanostructures Optical properties computer modelling and simulation Surface plasmon resonance (SPR)

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A computational and spectroscopic study of Dy³⁺ doped BaAl₂O₄ phosphors

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OPTICAL MATERIALS 2018年 83卷 328-332页

作者： Rezende, Marcos V. dos. S. Montes, Paulo J. R. Valerio, Mario E. G. Jackson, Robert A. Univ Fed Sergipe Dept Fis Grp Nanomat Funcionais GNF Campus Univ BR-49100000 Itabaiana SE Brazil Inst Fed Sergipe Coordenadoria Fis BR-49400000 Lagarto SE Brazil Univ Fed Sergipe Dept Fis Campus Univ BR-49100000 Sao Cristovao SE Brazil Keele Univ Sch Chem & Phys Sci Keele ST5 5BG Staffs England

Computational and experimental methods are employed to study the optical properties of Dy-doped BaAl2O4 matrix. Atomistic modelling is used to make predictions of Dy doping sites and charge compensation schemes. The symmetry predicts from atomistic modeling was used to calculate crystal field parameters and to obtain the energies of the electronic transitions of the Dy3+ ion. Dy-doped BaAl2O4 was prepared via a sol-gel proteic technique. The optical properties were studied using X-ray excited optical luminescence (XEOL) measurements. The X-ray absorption near-edge structure (XANES) at the Ba and Eu L-III-edges exhibits typical absorption spectra. The area under the XEOL spectra increases as the photon energy increases in the region around the Ba and Dy LIB-edges. The XEOL spectra showed typical Dy lines. Experimental and calculated values for the transition energies are compared. Computational and experimental methods are employed to study of Dy-doped BaAl2O4 matrix. Atomistic modelling is used to make predictions of Dy doping sites. The optical properties were studied using XEOL measurements.

关键词： Optical materials computer modelling and simulation Defects Optical properties Luminescence

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An Investigation into the Role of the Building Structure on Energy Use & CO2 Emissions over the Life Cycle of a Medium-Rise Residential Building

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IFAC-PapersOnLine 2018年第30期51卷 60-65页

作者： Nolan, Thomas Doyle-Kent, Mary Waterford Institute of Technology Cork Road Waterford City Ireland School of Engineering and the Built Environment Ireland

The shift towards Nearly Zero Energy Building (Nearly-ZEB) construction represents an attempt by the construction industry to limit the global warming potential of the sector. An investigation was carried out on how the structural frame of a low energy, residential, medium rise building is expected to affect energy use over the life cycle of the building. The feasibility of incorporating sustainable design constraints at the preliminary design is also assessed through the use of computer modelling and simulation methods. The findings of this paper show that by implementing simulation and knowledge management software, a life cycle approach to building construction can be adopted from the design conception stage. Results show that the building structure can influence life cycle energy use and carbon emissions. This information will provide an element of design control regarding environmental performance to Engineers across Europe from the early stages of the project. © 2016

关键词： Zero energy buildings Architectural design computer software Construction Construction industry Ecodesign Energy utilization Environmental impact Environmental management Global warming Housing Knowledge management Life cycle Sustainable development Building construction Building Information modelling computer modelling and simulation Environmental performance Global warming potential Life Cycle Assessment (LCA) Residential building simulation

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Massively parallel microscopic particle-in-cell

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computer PHYSICS COMMUNICATIONS 2017年 219卷 269-285页

作者： Bart, G. Peltz, C. Bigaouette, N. Fennel, T. Brabec, T. Varin, C. Univ Ottawa Dept Phys 150 Louis Pasteur Ottawa ON K1N 6N5 Canada Univ Rostock Inst Phys D-18051 Rostock Germany

The microscopic particle-in-cell (MicPIC) method was developed to model classical light matter interaction in strongly-coupled plasma systems. It effectively overcomes the limitations of the particle-in-cell and molecular dynamics techniques by combining them into a single, unified framework to solve for both electromagnetic wave propagation and atomic-scale collision processes in a self-consistent treatment. Its effective time complexity is O(N), where N is the number of model particles, which is ideal for studying the dynamics of large ensembles. In this paper, we show that through massively parallel, distributed computations, current implementations of the MicPIC approach can handle up to 10(11) particles on an IBM Blue Gene/Q computer with 65 536 physical cores. This allows modelling volumes of matter of approximately 1 mu m(3) at solid gold density, opening a wealth of potential applications of MicPIC in nanophotonics, diffractive X-ray imaging, and strong-field science. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Light matter interaction computer modelling and simulation Molecular dynamics calculations Particle-in-cell method

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